1. Field of the Invention
The present invention is concerned with aseptically operating packing machines and, in particular, relates to the design of the housing confining the sterile chamber of machines of this type, through which the web of packing material to be processed is guided under sterile conditions, when passed, for example, through preheating, moulding and filling stations.
2. Description of Prior Art
Irrespective of whether packing machines of this type are deep-drawing or tubular bag-type producing machines, the working elements of the afore-mentioned stations located in the sterile chamber will have to be operated externally, with the adjusting linkage thereof extending through the housing wall within a telescopic tube sealant, wherein the upper telescopic tube embraces the bottom telescopic tube seated stationarily on the housing, and is in communication with the appertaining drive.
Housings furnished with a telescopic tubular sealant of this type, hereinafter referred to as sterile tunnels or tubes, have been disclosed, for example, by European Patent Application 0727357. In this respect, a difference will have to be made between the normal operation of the packing machine (which in the afore-mentioned European Patent Application, is a deep-drawing packing machine) and the so-called pre-sterilization process always to be carried out following any interruption of operation. The said pre-sterilization is not effected by the sterile air permanently supplied during operation, but rather by another suitable sterilizing medium, such as a hydrogen peroxide finely divided within a corresponding fluid. In addition to areas other than those provided herefore, a minor part of the sterile air also during normal operation is discharged from the sterile tube through the telescopic tube sealant forming a discharge labyrinth for the sterile air, thereby also preventing the ingress of germs into the said telescopic tubular sealants from occurring. The same applies to sterilizing media supplied during the pre-sterilizing phase. The said sterilization is intended to safely eliminate the development of germs formed after a certain period of standstill of the packing machine concerned, within the sterile tunnel, the telescopic tubular sealant and all working elements contained therein. However, despite intensive pre-sterilizing efforts, germs consistently continued to develop in the sterile tube, even though to a minor extent. This fact which, initially, was inexplicable, virtually was found to be due to the telescopic tubular sealant which compared to other sealing types (bellow sealings, membrane sealings, vapor barriers or the like) is per se the most favourable one, because, on the one hand, the upper inner area of the upper telescopic tube, during the pre-sterilizing process, was suspected to be not entirely struck by the sterilizing fluid flowing therethrough and, on the other hand maintaining the telescopic tubular sealant which, per se is a satisfactory option, would prevent a solution to that problem from being attained, since the inverted cup shape of the telescopic tube was and is an inevitable condition.
It is an object of the present invention to so design the telescopic tube sealant on the sterile tubes of aseptically operating packing machines that during the pre-sterilizing phase, germs grown in the telescopic tubular sealant be safely struck and destroyed by the sterilizing fluid flowing therethrough.
Another object of the invention is to guide the flowing sterilizing fluid by simple, structural means through the labyrinth of the telescopic tubular sealant so as to strike all areas normally not or not completely struck.
In addition, it is an object of the invention to design the flow path through the labyrinth in such a manner that favourable conditions of flow are created.
This and other objects of the invention have been achieved in accordance with the invention in that an arrangement of the type described in the introduction part hereto was given the characteristic that apertures be circumferentially uniformly distributed in the upper area of the top telescopic tube for discharging the sterilizing fluid flowing from the sterile tunnel into the telescopic tube sealant.
This solution which is both simple and elegant promptly yielded the desired result, i.e. no germ formation otherwise occurred has developed any longer. Owing to the apertures now provided on the upper telescopic tube, an additional passageway for discharging the sterilizing fluid from the upper inner area of the top telescopic tube has been provided, which otherwise could only flow off through the annular gap between the upper and lower telescopic tubes, leaving, however, the upper interior area out of reach of the sterilizing fluid, i.e. germs formed there were not struck by the sterilizing fluid flowing therethrough.
In sterile tunnels wherein the upper telescopic tube is provided with a flange secured thereby to a carrier plate in communication with the associated drive (which is the standard design of telescopic tubular sealants of this type), the apertures confined by the carrier plate or the flange, are simply arranged within the said flange or carrier plate.
Another form of embodiment of the invention resides in that the top telescopic tube, at the upper end thereof, is closed by a plate in communication with the drive, with the said plate being provided with apertures. Moreover, the said apertures, in cross-section, can be of a slot-type configuration and in width can be so dimensioned that bridges are left between the slots that are narrower than the slot width.
To insure that the off-flowing sterilizing fluid does not take the path of least resistance through the annular gap between the upper and the lower telescopic tube, the apertures on the upper telescopic tube, in addition, are so dimensioned that the general cross-section thereof substantially corresponds to the one of the annular gap.
In conclusion, in the practice of the invention, provision can also be made for favourable flow conditions on the upper, inner limitation of the upper telescopic tube in that even minimum xe2x80x9cdead water cornersxe2x80x9d be avoided.
The above and other objects, features and advantages of the invention will become more apparent, and the invention itself will be understood, from the following description and appended claims, taken in connection with the attached drawings.